He defended legality of the election of Urban VI and his successors against the claims of the antipopes Clement VII and Benedict XIII.
As papal legate, Angelo crowned king Ladislaus of Naples in Gaeta on 29 May 1390.
He reformed the Benedictine monastery S. Paolo fuori le mura in Rome and participated in the papal conclave, 1404.
Newly elected Pope Innocent VII named him archpriest of the patriarchal Vatican Basilica (shortly after 4 December 1404), Cardinal-Bishop of Ostia e Velletri (12 June 1405), Dean of the Sacred College of Cardinals (12 June 1405), and finally Vice-Chancellor of the Holy Roman Church (on 29 August 1405).
In January 1394, King Ladislaus of Naples named him as his bailli and vicar-general for the Principality of Achaea and Lepanto.